A former longtime computer technician at the Lawrence Berkeley National Laboratory has been sentenced to 10 years in federal prison for downloading and viewing child pornography on his government computer.

David Busby, 61, of Richmond was convicted by a jury in September and sentenced Thursday by U.S. District Judge Saundra Brown Armstrong in Oakland. Federal law required the 10-year sentence because Busby had a previous sex crime conviction, for lewd behavior toward his 7-year-old stepdaughter in 1990.

Busby told officers he had downloaded child pornography and said he was "addicted" to porn, according to court filings in his case. Investigators said they found evidence that he had downloaded and later deleted about 1,400 child pornography images, but his lawyer told the jury Busby had accidentally downloaded the pornography while looking for legal sites.

Busby worked for the laboratory for 30 years and was also a 10-year Navy veteran who served in Vietnam, his public defender, Edward Smock, said in a court filing. He said Busby had been sexually abused as a child by his alcoholic father, an older brother and a neighborhood preacher, and had struggled to overcome his own alcoholism.